Accommodation compensation systems and methods

ABSTRACT

Methods and systems for obtaining an ocular aberration measurement of an eye of a patient are provided. Exemplary techniques involve obtaining a first induced metric for the eye that corresponds to a first accommodation state of the eye, obtaining a second induced metric for the eye that corresponds to a second accommodation state of the eye, and determining a natural metric of the eye based on the first and second induced metrics. An induced metric may include a pupil size or a spherical aberration. Techniques can also include determining a target metric for the eye base on the natural metric, determining whether an actual metric of the eye meets the target metric, obtaining an ocular aberration measurement of the eye if the actual metric meets the target metric, and determining a treatment for the eye based on the ocular aberration measurement.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/013,311 filed Aug. 29, 2013, which is a continuation of U.S. patentapplication Ser. No. 13/541,217 filed Jul. 3, 2012, which is acontinuation of U.S. patent application Ser. No. 13/276,704 filed Oct.19, 2011, which is a continuation of U.S. patent application Ser. No.13/012,298 filed Jan. 24, 2011, which is a continuation of U.S. patentapplication Ser. No. 12/126,185 filed May 23, 2008, which claims thebenefit of U.S. Provisional Patent Application No. 60/940,014 filed May24, 2007. The entire disclosure of each of these filings is incorporatedherein by reference for all purposes.

BACKGROUND OF THE INVENTION

Embodiments of the present invention relate to systems, devices, andmethods for compensating voluntary and other accommodation of patientsduring ocular diagnostic and treatment procedures. In particular,embodiments provide techniques for improving the accuracy of ocularaberration measurements and the development of vision correctiontreatments by evaluating accommodation in a patient.

An ocular wavefront measurement can change dramatically as the eyeaccommodates and the lens shape changes. This measurement change can bemanifested in a Hartmann-Shack spot pattern as a pincushion effect.Current wavefront-based refractometers often derive a patient's totalrefraction, or total ocular aberration, from a single measurement underthe assumption that accommodation has been effectively suppressed. Yetpatients can experience some degree of instrument myopia when suchmeasurements are taken, as the eye tends to accommodate inappropriatelywhen viewing though an optical instrument. For example, when a patientlooks through an optical instrument such as a refractometer or anaberrometer, the eye often responds by accommodating more than would benecessary for natural viewing. In some cases this excess accommodation,or instrument myopia, can be on the order of several diopters. As aresult, the effect of instrument myopia can lead to an inaccuratemeasurement of refraction.

A variety of approaches have been proposed to eliminate instrumentmyopia. In some cases, a doctor may try to simulate the object beingviewed, for example a viewing target, as far away from the patient aspossible such that the target is closer to optical infinity. When an eyeis gazing at a far distance the eye lens is thin and relaxed, andaccommodation is reduced. Another technique that attempts to cause eyeto relax the accommodation mechanism involves fogging. Fogging caninvolve adding a small amount of plus sphere power with a convexspherical lens, to provide a slight overcorrection. When the eye isoptically fogged, vision becomes blurrier as the eye accommodates, andthus accommodation is discouraged. Additional techniques involve askingthe patient to relax their vision. However many patients do not respondas desired to such approaches. Even when these accommodation-eliminationtechniques are implemented some instrument myopia may persist. What ismore, it is often difficult to determine whether the eye is accommodatedor not, particularly when a doctor or other instrument operator makingsuch a determination is inexperienced.

What is needed are systems and methods for reducing the amount ofinstrument myopia present in the eye during an optical measurement.Moreover, improved techniques are desired for determining residualaccommodation of the eye. Relatedly, there is a need for systems andmethods that can accurately determine whether a patient's eye isaccommodated, or the degree to which the patient's eye is accommodated.Embodiments of the present invention provide solutions to at least someof these problems.

BRIEF SUMMARY OF THE INVENTION

Systems, methods, and software are provided for compensating voluntaryaccommodation in a patient eye during a wavefront measurement. Theseapproaches can be used to improve the accuracy of the ocular aberrationmeasurement, and to improve the treatment of patients using laser visioncorrection of wavefront-driven procedures. Moreover, these approachescan be used to measure the residual accommodation of presbyopic patientsto customize or optimize a presbyopic treatment. Embodiments of thepresent invention provide improved techniques for evaluating theaccommodation state of a patient's eye, as well as for eliminating,reducing, or compensating for unwanted accommodation. For example,embodiments may encompass method and techniques for determining theamount of accommodation in an eye, determining the degree to which aneye is accommodated, the accommodation status of an eye, and the like.Similarly, embodiments encompass methods of designing optical treatmentshapes for vision correction, such as presbyopia refraction shapes,based on the accommodation characteristics of the patient eye. Theseshapes are well suited for implementation in any of a variety of visioncorrection modalities, including accommodating IOLs, custom IOLs,contact lenses, laser vision correction, and the like.

In a first aspect, embodiments of the present invention provide methodsof obtaining an ocular aberration measurement of an eye of a patient.Methods can include obtaining a first induced metric for the eye thatcorresponds to a first accommodation state of the eye, obtaining asecond induced metric for the eye that corresponds to a secondaccommodation state of the eye, and determining a natural metric of theeye based on the first and second induced metrics. In some cases, thefirst induced metric can include a first induced pupil size or a firstinduced spherical aberration, the second induced metric can include asecond induced pupil size or a second induced spherical aberration, andthe natural metric can include a natural pupil size or a naturalspherical aberration. Methods can also include determining a targetmetric for the eye base on the natural metric. A target metric caninclude a target pupil size or a target spherical aberration. In somecases, methods include determining whether an actual metric of the eyemeets the target metric. Methods can also include alerting an operatorif the actual metric does not meet the target metric. In some cases, anactual metric includes an actual pupil size or an actual sphericalaberration. Methods can also include obtaining an ocular aberrationmeasurement of the eye if the actual metric meets the target metric. Anocular aberration measurement can include a wavescan aberrometerexamination, a contact lens aberrometer examination, an IOL aberrometerexamination, or the like. In some cases, methods include determining atreatment for the eye based on the ocular aberration measurement.Methods can also include administering the treatment to the eye.

In another aspect, embodiments of the present invention encompassmethods of obtaining an ocular aberration measurement of an eye of apatient, which can involve obtaining a first induced metric for the eyethat corresponds to a first viewing condition, obtaining a secondinduced metric for the eye that corresponds to a second viewingcondition, determining a difference between the first induced metric andthe second induced metric, and determining an accommodationcharacteristic of the eye if the difference between the first inducedmetric and the second induced metric does not exceed a threshold. Insome cases, methods can include determining a target metric based on theaccommodation characteristic, determining whether an actual metric ofthe eye meets the target metric, and obtaining an ocular aberrationmeasurement of the eye if the actual metric meets the target metric. Insome cases, a first induced metric includes a first induced pupil size,a second induced metric includes a second induced pupil size, and anaccommodation characteristic includes a minimally accommodated pupilsize. A target metric can include a target pupil size, and an actualmetric can include an actual pupil size. A first induced metric caninclude a first induced spherical aberration, a second induced metriccan include a second induced spherical aberration, and an accommodationcharacteristic can include an minimally accommodated sphericalaberration. In some cases, a target metric includes a target sphericalaberration, and an actual metric includes an actual sphericalaberration. An ocular aberration measurement can include, for example, awavescan aberrometer examination, a contact lens aberrometerexamination, an IOL aberrometer examination, or the like. In some cases,methods include alerting an operator if the actual metric does not meetthe target metric. Methods can also include determining a treatment forthe eye based on an ocular aberration measurement. Similarly, methodscan include administering the treatment to the eye.

In some aspects, embodiments of the present invention encompass methodsof determining a presbyopia treatment for an eye of a patient. Methodscan include, for example, obtaining a first induced metric for the eyethat corresponds to a first viewing condition, obtaining a secondinduced metric for the eye that corresponds to a second viewingcondition, determining a difference between the first induced metric andthe second induced metric, determining an accommodation characteristicof the eye if the difference between the first induced metric and thesecond induced metric does not exceed a threshold, determining aresidual accommodation of the eye based on the accommodationcharacteristic, obtaining an ocular aberration measurement of the eye,and determining a presbyopia treatment for the eye based on the residualaccommodation and the ocular aberration measurement. In some cases, afirst induced metric includes a first induced pupil size, a secondinduced metric includes a second induced pupil size, an accommodationcharacteristic includes a maximally accommodated pupil size, a targetmetric includes a target pupil size, and an actual metric includes anactual pupil size. A first induced metric can include a first inducedspherical aberration, a second induced metric can include a secondinduced spherical aberration, an accommodation characteristic caninclude an maximally accommodated spherical aberration, a target metriccan include a target spherical aberration, and an actual metric caninclude an actual spherical aberration. An ocular aberration measurementcan include a wavescan aberrometer examination, a contact lensaberrometer examination, an IOL aberrometer examination, or the like. Insome cases, methods include administering the presbyopia treatment tothe eye.

In another aspect, embodiments of the present invention include systemsfor obtaining an ocular aberration measurement of an eye of a patient. Asystem may include, for example, a first input configured to receive afirst induced metric for the eye that corresponds to a firstaccommodation state of the eye, a second input configured to receive asecond induced metric for the eye that corresponds to a secondaccommodation state of the eye, and a module configured to determine anatural metric of the eye based on the first and second induced metrics.A first induced metric can include a first induced pupil size or a firstinduced spherical aberration, a second induced metric can include asecond induced pupil size or a second induced spherical aberration, anda natural metric can include a natural pupil size or a natural sphericalaberration.

In a further aspect, embodiments of the present invention includesystems for obtaining an ocular aberration measurement of an eye of apatient, which can include a first input configured to receive a firstinduced metric for the eye that corresponds to a first viewingcondition, a second input configured to receive a second induced metricfor the eye that corresponds to a second viewing condition, a firstmodule configured to determine a difference between the first inducedmetric and the second induced metric, and a second module configured todetermine an accommodation characteristic of the eye if the differencebetween the first induced metric and the second induced metric does notexceed a threshold. In some cases, systems can include a moduleconfigured to determine a target metric based on the accommodationcharacteristic, a module configured to determine whether an actualmetric of the eye meets the target metric, and a module configured toreceive an ocular aberration measurement of the eye if the actual metricmeets the target metric.

In some aspects, embodiments of the present invention encompass systemsfor determining a presbyopia treatment for an eye of a patient. Systemscan include, for example, an input configured to receive a first inducedmetric for the eye that corresponds to a first viewing condition, aninput configured to receive a second induced metric for the eye thatcorresponds to a second viewing condition, a module configured todetermine a difference between the first induced metric and the secondinduced metric, a module configured to determine an accommodationcharacteristic of the eye if the difference between the first inducedmetric and the second induced metric does not exceed a threshold, amodule configured to determine a residual accommodation of the eye basedon the accommodation characteristic, a module configured to receive anocular aberration measurement of the eye, and a module configured todetermine a presbyopia treatment for the eye based on the residualaccommodation and the ocular aberration measurement.

In some aspect, embodiments of the present invention provide a method ofobtaining a residual accommodation measurement of an eye of a patient.The method may include, for example, obtaining a first induced metricfor the eye that corresponds to a first viewing condition, obtaining asecond induced metric for the eye that corresponds to a second viewingcondition, determining if a difference between the first induced metricand the second induced metric exceeds a threshold, determining anaccommodation characteristic of the eye if the difference between thefirst induced metric and the second induced metric does not exceed thethreshold, and determining the residual accommodation measurement of theeye based on the accommodation characteristic. In some cases, the firstinduced metric comprises a first induced pupil size, the second inducedmetric comprises a second induced pupil size, and the accommodationcharacteristic comprises a maximally accommodated pupil size. In somecases, the first induced metric comprises a first induced sphericalaberration, the second induced metric comprises a second inducedspherical aberration, and the accommodation characteristic comprises amaximally accommodated spherical aberration.

In some aspects, embodiments of the present invention provide a methodof determining a natural metric of an unaccommodated eye. The method mayinclude, for example, inputting a first induced metric for the eye thatcorresponds to a first accommodation state of the eye, inputting asecond induced metric for the eye that corresponds to a secondaccommodation state of the eye, and determining the natural metric ofthe unaccommodated or minimally accommodated eye based on the first andsecond induced metrics and the first and second accommodation states ofthe eye. For example, the first and second induced metrics can be inputinto an input module, and the natural metric can be determined by adetermination module. The natural metric can be an aberration metric ora pupil size metric. Optionally, the method may include inputting threeor more induced metrics corresponding to respective accommodation statesof the eye, and determining the natural metric of the unaccommodated orminimally accommodated eye based on a combination of two or more of theinduced metrics. The aberration metric can be a spherical aberrationmetric, a sphere metric, or a coma metric. The method may also includedetermining a target metric for the unaccommodated or minimallyaccommodated eye based on the natural metric. Further, the method mayinclude determining an actual metric of the eye. In some cases, themethod may include determining whether the actual metric meets thetarget metric. The method may also include obtaining an ocularaberration measurement of the eye if the natural metric meets a targetmetric. The ocular aberration measurement can include, for example, awavescan measurement. In some cases, the unaccommodated or minimallyaccommodated eye has a power of zero diopters.

In some aspects, embodiments encompass a method of determining a naturalpupil size metric of an unaccommodated or minimally accommodated eye.The method can include inputting a first induced pupil size metric forthe eye that corresponds to a first accommodation state of the eye,inputting a second induced pupil size metric for the eye thatcorresponds to a second accommodation state of the eye, and determiningthe natural pupil size metric of the unaccommodated or minimallyaccommodated eye based on the first and second induced pupil sizemetrics and the first and second accommodation states of the eye.

For a fuller understanding of the nature and advantages of the presentinvention, reference should be had to the ensuing detailed descriptiontaken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a laser ablation system according to an embodiment ofthe present invention.

FIG. 2 illustrates a simplified computer system according to anembodiment of the present invention.

FIG. 3 illustrates a wavefront measurement system according to anembodiment of the present invention.

FIG. 3A illustrates another wavefront measurement system according to anembodiment of the present invention.

FIG. 4 schematically illustrates method embodiments of the presentinvention.

FIG. 5 depicts methods aspects of exemplary embodiments of the presentinvention.

FIGS. 6A-6C illustrate the effects of changing focal distance on apatient's lens, according to embodiments of the present invention.

FIGS. 7A-7E illustrate relationships involving ocular characteristics ofan eye according to embodiments of the present invention.

FIG. 8 depicts relationships between accommodation, pupil size, and netspherical aberration according to embodiments of the present invention.

FIG. 9 depicts relationships between accommodation, pupil size, and netspherical aberration according to embodiments of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention can be readily adapted for use with existing lasersystems, wavefront measurement systems, and other optical measurementdevices. Although the systems, software, and methods of the presentinvention are described primarily in the context of a laser eye surgerysystem, it should be understood the present invention may be adapted foruse in alternative eye treatment procedures, systems, or modalities,such as spectacle lenses, intraocular lenses, accommodating IOLs,contact lenses, corneal ring implants, collagenous corneal tissuethermal remodeling, corneal inlays, corneal onlays, other cornealimplants or grafts, and the like. Relatedly, systems, software, andmethods according to embodiments of the present invention are wellsuited for customizing any of these treatment modalities to a specificpatient. Thus, for example, embodiments encompass custom intraocularlenses, custom contact lenses, custom corneal implants, and the like,which can be configured to treat or ameliorate any of a variety ofvision conditions in a particular patient based on their unique ocularcharacteristics or anatomy.

Turning now to the drawings, FIG. 1 illustrates a laser eye surgerysystem 10 of the present invention, including a laser 12 that produces alaser beam 14. Laser 12 is optically coupled to laser delivery optics16, which directs laser beam 14 to an eye E of patient P. A deliveryoptics support structure (not shown here for clarity) extends from aframe 18 supporting laser 12. A microscope 20 is mounted on the deliveryoptics support structure, the microscope often being used to image acornea of eye E.

Laser 12 generally comprises an excimer laser, ideally comprising anargon-fluorine laser producing pulses of laser light having a wavelengthof approximately 193 nm. Laser 12 will preferably be designed to providea feedback stabilized fluence at the patient's eye, delivered viadelivery optics 16. The present invention may also be useful withalternative sources of ultraviolet or infrared radiation, particularlythose adapted to controllably ablate the corneal tissue without causingsignificant damage to adjacent and/or underlying tissues of the eye.Such sources include, but are not limited to, solid state lasers andother devices which can generate energy in the ultraviolet wavelengthbetween about 185 and 205 nm and/or those which utilizefrequency-multiplying techniques. Hence, although an excimer laser isthe illustrative source of an ablating beam, other lasers may be used inthe present invention.

Laser system 10 will generally include a computer or programmableprocessor 22. Processor 22 may comprise (or interface with) aconventional PC system including the standard user interface devicessuch as a keyboard, a display monitor, and the like. Processor 22 willtypically include an input device such as a magnetic or optical diskdrive, an internet connection, or the like. Such input devices willoften be used to download a computer executable code from a tangiblestorage media 29 embodying any of the methods of the present invention.Tangible storage media 29 may take the form of a floppy disk, an opticaldisk, a data tape, a volatile or non-volatile memory, RAM, or the like,and the processor 22 will include the memory boards and other standardcomponents of modern computer systems for storing and executing thiscode. Tangible storage media 29 may optionally embody wavefront sensordata, wavefront gradients, a wavefront elevation map, a treatment map, acorneal elevation map, and/or an ablation table. While tangible storagemedia 29 will often be used directly in cooperation with an input deviceof processor 22, the storage media may also be remotely operativelycoupled with processor by means of network connections such as theinternet, and by wireless methods such as infrared, Bluetooth, or thelike.

Laser 12 and delivery optics 16 will generally direct laser beam 14 tothe eye of patient P under the direction of a computer 22. Computer 22will often selectively adjust laser beam 14 to expose portions of thecornea to the pulses of laser energy so as to effect a predeterminedsculpting of the cornea and alter the refractive characteristics of theeye. In many embodiments, both laser beam 14 and the laser deliveryoptical system 16 will be under computer control of processor 22 toeffect the desired laser sculpting process, with the processor effecting(and optionally modifying) the pattern of laser pulses. The pattern ofpulses may by summarized in machine readable data of tangible storagemedia 29 in the form of a treatment table, and the treatment table maybe adjusted according to feedback input into processor 22 from anautomated image analysis system in response to feedback data providedfrom an ablation monitoring system feedback system. Optionally, thefeedback may be manually entered into the processor by a systemoperator. Such feedback might be provided by integrating the wavefrontmeasurement system described below with the laser treatment system 10,and processor 22 may continue and/or terminate a sculpting treatment inresponse to the feedback, and may optionally also modify the plannedsculpting based at least in part on the feedback. Measurement systemsare further described in U.S. Pat. No. 6,315,413, the full disclosure ofwhich is incorporated herein by reference.

Laser beam 14 may be adjusted to produce the desired sculpting using avariety of alternative mechanisms. The laser beam 14 may be selectivelylimited using one or more variable apertures. An exemplary variableaperture system having a variable iris and a variable width slit isdescribed in U.S. Pat. No. 5,713,892, the full disclosure of which isincorporated herein by reference. The laser beam may also be tailored byvarying the size and offset of the laser spot from an axis of the eye,as described in U.S. Pat. Nos. 5,683,379, 6,203,539, and 6,331,177, thefull disclosures of which are incorporated herein by reference.

Still further alternatives are possible, including scanning of the laserbeam over the surface of the eye and controlling the number of pulsesand/or dwell time at each location, as described, for example, by U.S.Pat. No. 4,665,913, the full disclosure of which is incorporated hereinby reference; using masks in the optical path of laser beam 14 whichablate to vary the profile of the beam incident on the cornea, asdescribed in U.S. Pat. No. 5,807,379, the full disclosure of which isincorporated herein by reference; hybrid profile-scanning systems inwhich a variable size beam (typically controlled by a variable widthslit and/or variable diameter iris diaphragm) is scanned across thecornea; or the like. The computer programs and control methodology forthese laser pattern tailoring techniques are well described in thepatent literature.

Additional components and subsystems may be included with laser system10, as should be understood by those of skill in the art. For example,spatial and/or temporal integrators may be included to control thedistribution of energy within the laser beam, as described in U.S. Pat.No. 5,646,791, the full disclosure of which is incorporated herein byreference. Ablation effluent evacuators/filters, aspirators, and otherancillary components of the laser surgery system are known in the art.Further details of suitable systems for performing a laser ablationprocedure can be found in commonly assigned U.S. Pat. Nos. 4,665,913,4,669,466, 4,732,148, 4,770,172, 4,773,414, 5,207,668, 5,108,388,5,219,343, 5,646,791 and 5,163,934, the complete disclosures of whichare incorporated herein by reference. Suitable systems also includecommercially available refractive laser systems such as thosemanufactured and/or sold by Alcon, Bausch & Lomb, Nidek, WaveLight,LaserSight, Schwind, Zeiss-Meditec, and the like. Basis data can befurther characterized for particular lasers or operating conditions, bytaking into account localized environmental variables such astemperature, humidity, airflow, and aspiration.

FIG. 2 is a simplified block diagram of an exemplary computer system 22that may be used by the laser surgical system 10 of the presentinvention. Computer system 22 typically includes at least one processor52 which may communicate with a number of peripheral devices via a bussubsystem 54. These peripheral devices may include a storage subsystem56, comprising a memory subsystem 58 and a file storage subsystem 60,user interface input devices 62, user interface output devices 64, and anetwork interface subsystem 66. Network interface subsystem 66 providesan interface to outside networks 68 and/or other devices, such as thewavefront measurement system 30.

User interface input devices 62 may include a keyboard, pointing devicessuch as a mouse, trackball, touch pad, or graphics tablet, a scanner,foot pedals, a joystick, a touchscreen incorporated into the display,audio input devices such as voice recognition systems, microphones, andother types of input devices. User input devices 62 will often be usedto download a computer executable code from a tangible storage media 29embodying any of the methods of the present invention. In general, useof the term “input device” is intended to include a variety ofconventional and proprietary devices and ways to input information intocomputer system 22.

User interface output devices 64 may include a display subsystem, aprinter, a fax machine, or non-visual displays such as audio outputdevices. The display subsystem may be a cathode ray tube (CRT), aflat-panel device such as a liquid crystal display (LCD), a projectiondevice, or the like. The display subsystem may also provide a non-visualdisplay such as via audio output devices. In general, use of the term“output device” is intended to include a variety of conventional andproprietary devices and ways to output information from computer system22 to a user.

Storage subsystem 56 can store the basic programming and data constructsthat provide the functionality of the various embodiments of the presentinvention. For example, a database and modules implementing thefunctionality of the methods of the present invention, as describedherein, may be stored in storage subsystem 56. These software modulesare generally executed by processor 52. In a distributed environment,the software modules may be stored on a plurality of computer systemsand executed by processors of the plurality of computer systems. Storagesubsystem 56 typically comprises memory subsystem 58 and file storagesubsystem 60.

Memory subsystem 58 typically includes a number of memories including amain random access memory (RAM) 70 for storage of instructions and dataduring program execution and a read only memory (ROM) 72 in which fixedinstructions are stored. File storage subsystem 60 provides persistent(non-volatile) storage for program and data files, and may includetangible storage media 29 (FIG. 1) which may optionally embody wavefrontsensor data, wavefront gradients, a wavefront elevation map, a treatmentmap, and/or an ablation table. File storage subsystem 60 may include ahard disk drive, a floppy disk drive along with associated removablemedia, a Compact Digital Read Only Memory (CD-ROM) drive, an opticaldrive, DVD, CD-R, CD-RW, solid-state removable memory, and/or otherremovable media cartridges or disks. One or more of the drives may belocated at remote locations on other connected computers at other sitescoupled to computer system 22. The modules implementing thefunctionality of the present invention may be stored by file storagesubsystem 60.

Bus subsystem 54 provides a mechanism for letting the various componentsand subsystems of computer system 22 communicate with each other asintended. The various subsystems and components of computer system 22need not be at the same physical location but may be distributed atvarious locations within a distributed network. Although bus subsystem54 is shown schematically as a single bus, alternate embodiments of thebus subsystem may utilize multiple busses.

Computer system 22 itself can be of varying types including a personalcomputer, a portable computer, a workstation, a computer terminal, anetwork computer, a control system in a wavefront measurement system orlaser surgical system, a mainframe, or any other data processing system.Due to the ever-changing nature of computers and networks, thedescription of computer system 22 depicted in FIG. 2 is intended only asa specific example for purposes of illustrating one embodiment of thepresent invention. Many other configurations of computer system 22 arepossible having more or less components than the computer systemdepicted in FIG. 2.

Referring now to FIG. 3, one embodiment of a wavefront measurementsystem 30 is schematically illustrated in simplified form. In verygeneral terms, wavefront measurement system 30 is configured to senselocal slopes of a gradient map exiting the patient's eye. Devices basedon the Hartmann-Shack principle generally include a lenslet array tosample the gradient map uniformly over an aperture, which is typicallythe exit pupil of the eye. Thereafter, the local slopes of the gradientmap are analyzed so as to reconstruct the wavefront surface or map.

More specifically, one wavefront measurement system 30 includes an imagesource 32, such as a laser, which projects a source image throughoptical tissues 34 of eye E so as to form an image 44 upon a surface ofretina R. The image from retina R is transmitted by the optical systemof the eye (e.g., optical tissues 34) and imaged onto a wavefront sensor36 by system optics 37. The wavefront sensor 36 communicates signals toa computer system 22′ for measurement of the optical errors in theoptical tissues 34 and/or determination of an optical tissue ablationtreatment program. Computer 22′ may include the same or similar hardwareas the computer system 22 illustrated in FIGS. 1 and 2. Computer system22′ may be in communication with computer system 22 that directs thelaser surgery system 10, or some or all of the components of computersystem 22, 22′ of the wavefront measurement system 30 and laser surgerysystem 10 may be combined or separate. If desired, data from wavefrontsensor 36 may be transmitted to a laser computer system 22 via tangiblemedia 29, via an I/O port, via an networking connection 66 such as anintranet or the Internet, or the like.

Wavefront sensor 36 generally comprises a lenslet array 38 and an imagesensor 40. As the image from retina R is transmitted through opticaltissues 34 and imaged onto a surface of image sensor 40 and an image ofthe eye pupil P is similarly imaged onto a surface of lenslet array 38,the lenslet array separates the transmitted image into an array ofbeamlets 42, and (in combination with other optical components of thesystem) images the separated beamlets on the surface of sensor 40.Sensor 40 typically comprises a charged couple device or “CCD,” andsenses the characteristics of these individual beamlets, which can beused to determine the characteristics of an associated region of opticaltissues 34. In particular, where image 44 comprises a point or smallspot of light, a location of the transmitted spot as imaged by a beamletcan directly indicate a local gradient of the associated region ofoptical tissue.

Eye E generally defines an anterior orientation ANT and a posteriororientation POS. Image source 32 generally projects an image in aposterior orientation through optical tissues 34 onto retina R asindicated in FIG. 3. Optical tissues 34 again transmit image 44 from theretina anteriorly toward wavefront sensor 36. Image 44 actually formedon retina R may be distorted by any imperfections in the eye's opticalsystem when the image source is originally transmitted by opticaltissues 34. Optionally, image source projection optics 46 may beconfigured or adapted to decrease any distortion of image 44.

In some embodiments, image source optics 46 may decrease lower orderoptical errors by compensating for spherical and/or cylindrical errorsof optical tissues 34. Higher order optical errors of the opticaltissues may also be compensated through the use of an adaptive opticelement, such as a deformable mirror (described below). Use of an imagesource 32 selected to define a point or small spot at image 44 uponretina R may facilitate the analysis of the data provided by wavefrontsensor 36. Distortion of image 44 may be limited by transmitting asource image through a central region 48 of optical tissues 34 which issmaller than a pupil 50, as the central portion of the pupil may be lessprone to optical errors than the peripheral portion. Regardless of theparticular image source structure, it will be generally be beneficial tohave a well-defined and accurately formed image 44 on retina R.

In one embodiment, the wavefront data may be stored in a computerreadable medium 29 or a memory of the wavefront sensor system 30 in twoseparate arrays containing the x and y wavefront gradient valuesobtained from image spot analysis of the Hartmann-Shack sensor images,plus the x and y pupil center offsets from the nominal center of theHartmann-Shack lenslet array, as measured by the pupil camera 51 (FIG.3) image. Such information contains all the available information on thewavefront error of the eye and is sufficient to reconstruct thewavefront or any portion of it. In such embodiments, there is no need toreprocess the Hartmann-Shack image more than once, and the data spacerequired to store the gradient array is not large. For example, toaccommodate an image of a pupil with an 8 mm diameter, an array of a20×20 size (i.e., 400 elements) is often sufficient. As can beappreciated, in other embodiments, the wavefront data may be stored in amemory of the wavefront sensor system in a single array or multiplearrays.

While the methods of the present invention will generally be describedwith reference to sensing of an image 44, a series of wavefront sensordata readings may be taken. For example, a time series of wavefront datareadings may help to provide a more accurate overall determination ofthe ocular tissue aberrations. As the ocular tissues can vary in shapeover a brief period of time, a plurality of temporally separatedwavefront sensor measurements can avoid relying on a single snapshot ofthe optical characteristics as the basis for a refractive correctingprocedure. Still further alternatives are also available, includingtaking wavefront sensor data of the eye with the eye in differingconfigurations, positions, and/or orientations. For example, a patientwill often help maintain alignment of the eye with wavefront measurementsystem 30 by focusing on a fixation target, as described in U.S. Pat.No. 6,004,313, the full disclosure of which is incorporated herein byreference. By varying a position of the fixation target as described inthat reference, optical characteristics of the eye may be determinedwhile the eye accommodates or adapts to image a field of view at avarying distance and/or angles.

The location of the optical axis of the eye may be verified by referenceto the data provided from a pupil camera 52. In the exemplaryembodiment, a pupil camera 52 images pupil 50 so as to determine aposition of the pupil for registration of the wavefront sensor datarelative to the optical tissues.

An alternative embodiment of a wavefront measurement system isillustrated in FIG. 3A. The major components of the system of FIG. 3Aare similar to those of FIG. 3. Additionally, FIG. 3A includes anadaptive optical element 53 in the form of a deformable mirror. Thesource image is reflected from deformable mirror 98 during transmissionto retina R, and the deformable mirror is also along the optical pathused to form the transmitted image between retina R and imaging sensor40. Deformable mirror 98 can be controllably deformed by computer system22 to limit distortion of the image formed on the retina or ofsubsequent images formed of the images formed on the retina, and mayenhance the accuracy of the resultant wavefront data. The structure anduse of the system of FIG. 3A are more fully described in U.S. Pat. No.6,095,651, the full disclosure of which is incorporated herein byreference.

The components of an embodiment of a wavefront measurement system formeasuring the eye and ablations may comprise elements of a WaveScan®system, available from VISX, INCORPORATED of Santa Clara, Calif. Oneembodiment includes a WaveScan system with a deformable mirror asdescribed above. An alternate embodiment of a wavefront measuring systemis described in U.S. Pat. No. 6,271,915, the full disclosure of which isincorporated herein by reference. It is appreciated that any wavefrontaberrometer could be employed for use with the present invention.Relatedly, embodiments of the present invention encompass theimplementation of any of a variety of optical instruments provided byWaveFront Sciences, Inc., including the COAS wavefront aberrometer, theClearWave contact lens aberrometer, the CrystalWave IOL aberrometer, andthe like.

In some embodiments, an aberrometer device can be used to measure wholeeye spherical aberration (SA), and a topography device can be used toobtain a topography or spherical aberration of a cornea. Based on thewhole eye SA and the cornea SA, the SA of the lens can be calculated.The change or difference in SA due to a natural lens or an accommodatingIOL can be determined. Hence, accommodation can be measured. A wavefrontmay change as it propagates from one plane to another. Thus, topographicaberrations of the cornea can be represented at the exit pupil plane,and aberrations of the entire eye can be represented at the exit pupilplane. When deriving a difference between an ocular aberration and acorneal aberration, the difference may be represented at the exit pupilplane. When using the difference to determine an aberration of a naturallens or an accommodating IOL, the representation of the aberration maybe translated, for example, to an IOL plane. Wavefront propagationconversions are discussed in co-pending and co-owned patent applicationSer. No. 11/736,353 filed Apr. 17, 2007, the entire contents of whichare hereby incorporated by reference for all purposes.

Embodiments of the present invention provide systems, methods, anddevices for compensating voluntary accommodation of patients duringwavefront measurements. These techniques can be used to improve theaccuracy of the ocular aberration measurements and to improve thetreatment of patients using laser vision correction treatments based onwavefront procedures. Such approaches can also be used to measure theresidual accommodation of presbyopic patients and to customize treatmentfor such patients.

It is often difficult with some current techniques to achieve completeor desired lack of accommodation in a patient. For example, some haveestimated that about 5% of the patient population presents unwantedaccommodation during optical testing and treatment procedures. Thetechniques disclosed herein provide improved systems and methods thatcompel a patient's eye away from an accommodated state and toward anunaccommodated or deaccommodated state.

The amplitude of accommodation can be defined as the eye's ability tofocus at near. A child's eye may be able to focus at about 2-3 inches,which corresponds to an amplitude of accommodation of about 10-30diopters. In contrast, a 45 year old person may only be able to focus atabout 20 inches, which corresponds to an amplitude of accommodation ofabout 2 diopters.

FIG. 4 schematically illustrates method embodiments of the presentinvention. These methods involve evaluating accommodationcharacteristics of a patient's eye, and determining corrective oculartreatments for the eye. Step 80 involves determining a natural metric ofan eye. A natural metric of the eye can include, for example, thenatural pupil size of the eye or the natural spherical aberration of theeye. Often, the term natural metric refers to a characteristic of theeye under natural conditions, in the absence of influences that may bepresent during diagnostic or testing procedures. For example, this termmay indicate the pupil size of the eye when the patient is not subjectto a particular diagnostic instrument. Accordingly, this term can berelated to the status of the eye where instrument myopia is absent orreduced.

The patient eye metric can include a pupil size or a sphericalaberration, as noted above. Patient eye metrics may also include coma ortrefoil. More broadly, metrics suitable for use with embodiments of thepresent invention include low order aberrations, high order aberrations,primary or secondary astigmatism, primary or secondary coma, primary orsecondary sphere, primary or secondary spherical aberration, pupil size,defocus, root mean square, high order root mean square with an error,and the like. Metrics may also encompass combinations, for example ametric may include coma and trefoil, which are third order aberrations.Similarly, a metric may include secondary astigmatism, sphericalaberration, and quadrafoil, which are fourth order aberrations. Metricembodiments also encompass fifth order aberrations, sixth orderaberrations, and the like. Such optical metrics may change as theaccommodation of the eye increases or decreases. For example, thespherical aberration of the eye may increase as the eye changes toward amore accommodated state. The rate and magnitude of these metric changesoften vary from patient to patient, and can even vary between eyes in asingle patient.

Certain individuals within a population may present ocularcharacteristics which vary from the norm or from other individualswithin the population. For example, it has been observed what withinsome populations, about 90 percent of the individuals present a naturalspherical aberration that is positive, and about 10 percent of theindividuals present a natural spherical aberration that is negative,when the eye is relaxed or unaccommodated. In some embodiments, metricscan be determined or evaluated with respect to ocular characteristicsexhibited by a population or set of individuals. For example, a metriccan be based on an average or mean pupil size of a group of individuals.Similarly, a metric can be based on an average or mean sphericalaberration of a group of individuals. Relatedly, a diagnosis ortreatment can be based on ocular characteristics of a population orsubset thereof, in addition to or instead of a patient's particularocular characteristic. In one embodiment, a patient treatment based on amean value of spherical aberration from a population of individuals. Insome cases, the mean value of spherical aberration from a population ofindividuals is determined based on a standardized pupil size. That is,within the population of individuals it is possible to characterize aspherical aberration characteristic with respect to a pupil size. Thus,a population mean spherical aberration can be associated with pupilsize. A treatment for an individual patient can involve a pupil sizenormalization. Relatedly, it is possible to tailor a patient treatmentbased on a pupil size of the patient, and a mean value of sphericalaberration from a population of individuals. For example, a treatmentcan be scaled based on the patient pupil size and the population mean.

When a patient eye fully or maximally unaccommodates during a wavefrontmeasurement, the pupil size is relatively large. When the eyeaccommodates, the pupil constricts and often can be about 1.5 mm smallerthan the unaccommodated pupil size. In some embodiments, a wavescanmeasurement can be performed under low light. When evaluating apatient's eye under low light, for example with an aberrometer, thepupil size is large or at or near its maximum. It may be desirable tocapture or evaluation ocular aberrations of the patient's eye when thepupil is enlarged. If an examination is performed under intense light orwhen the pupil is constricted, there may be aberration information thatis outside of the capture area that is missed. Evaluating the eye underlow light can improve the likelihood of obtaining a reliable aberrationrepresentation for pupil dynamics when the pupil constricts.

Step 82 involves determining a minimum accommodation characteristic ofthe eye. The term minimum accommodation characteristic can include acharacteristic of the eye that corresponds to the eye when in aminimally accommodated state. For example, a minimum accommodationcharacteristic can be a pupil size of the eye when the eye is minimallyaccommodated. This step can involve compelling a patient's eye toward anunaccommodated state, and concomitantly evaluating the accommodationstatus of the eye. A minimum accommodation characteristic reflects thestate of the eye where further deaccommodation is difficult or no longerpossible.

Step 84 includes determining a target metric based on the natural metricor the minimum accommodation characteristic. Step 86 includesdetermining the actual metric of the eye, and step 88 includesdetermining whether the actual metric meets the target metric. Thesesteps involve a pre-testing or pre-examination approach whereby anaccommodation status of the eye is evaluated prior to determiningwhether to proceed with a wavefront or other refractometer measurement.For example, it is possible to determine a pupil size of the eye thatcorresponds to the eye in a minimally accommodated state. The eye isthen evaluated prior to a wavefront exam. If the pupil size of the eyeis sufficiently different from the minimally accommodated pupil size, orsufficiently different from a target metric based on the minimallyaccommodated pupil size, then a decision can be made not to proceed withthe wavefront measurement. If, however, the actual pupil size issufficiently close to the minimally accommodated pupil size, orsufficiently close to a target metric based on the minimallyaccommodated pupil size, then a decision can be made to proceed with thewavefront measurement. Accordingly, step 90 involves obtaining awavefront measurement with a WaveScan wavefront diagnostic system anddetermining an optical treatment, such as a CustomVue treatment, basedon the measurement. Optionally, a procedure may include determining amaximum accommodation characteristic of a patient eye, as indicated bystep 92. A presbyopia treatment can be determined based on the maximumaccommodation characteristic of the eye, as indicated by step 94.

FIG. 5 provides a detailed illustration of method embodiments of thepresent invention. In a first prong, method 500 includes obtaining afirst induced metric for the eye that corresponds to a firstaccommodation state of the eye, as indicated by step 100. The firstinduced metric can include, for example, a pupil size of the eye or aspherical aberration of the eye. The pupil size can be measured by anyof a variety of instruments, such as a video camera. The sphericalaberration can be measured by an aberrometer such as a Hartmann-Shackdevice. Step 105 involves obtaining a second induced metric for the eyethat corresponds to a second accommodation state of the eye. The secondinduced metric can include, for example, a pupil size of the eye or aspherical aberration of the eye.

This approach often involves physically pushing the eye toward a lessaccommodated state, or toward a more accommodated state, and monitoringthe associated changes in the induced metric to determine whether or towhat extent the eye is accommodated. In this way, it is possible toascertain a model that predicts or determines the natural metric, whichmay correspond to an unaccommodated state of the eye. Any of a varietyof stimuli or optical testing apparatuses can be used to compelaccommodation changes in the pupil eye, including trial lenses, movingtarget, stimulated moving targets, and the like. A trial lens systemmay, for example, be used to simulate various target distances. Triallenses can incorporate sphere, cylinder, or other properties. Thistechnique often does not involve physically pushing the eye to thecompletely unaccommodated or accommodated state, however. Based on thisapproach it is possible to determine a relationship between the level ofaccommodation and the metric (e.g. pupil size, spherical aberrations, orvergence). In some cases, this relationship may be a linearrelationship. In other cases, the relationship may be quadratic,logarithmic, exponential, or the like. Typically, the relationship islinear across a patient population.

Step 110 includes determining a natural metric of the eye based on thefirst and second induced metrics. The natural metric can be, forexample, a pupil size or a spherical aberration for the eye when it isin an unaccommodated state. Similarly, the natural metric can be a pupilsize or a spherical aberration for the eye when it is in a minimallyaccommodated state, a maximally accommodated state, or a partiallyaccommodated state. As noted above, a natural metric refers to acharacteristic of the eye under natural conditions, in the absence ofinfluences that may be present during diagnostic or testing procedures.For example, the natural metric may refer to an eye characteristic inthe absence of a stimulus or other optical testing apparatus. In somecases, this corresponds to a situation where there is no trial lens, orwhere the amount of the trial lens power does not provide a stimulus orinduce an unwanted amount of defocus. Similarly, the intensity of theambient light can be adjusted or maintained so as to not provide astimulus. Step 120 encompasses determining a target metric for the eyebased on the natural metric. The target metric can be, for example, atarget pupil size or a target spherical aberration of the eye. In asecond prong, method 500 includes obtaining an induced metric for theeye that corresponds to a viewing condition, as indicated by step 200.The method can also include adjusting the viewing condition, as shown bystep 205. The viewing condition can be adjusted, for example, byadjusting a trial lens, by adjusting a target distance, by adjusting asimulated target distance, and the like. Step 210 includes obtaining aninduced metric for the eye that corresponds to the adjusted viewingcondition. These induced metrics can include, for example, a pupil sizeor a spherical aberration of the eye of the patient.

In some cases, this technique can include subjecting the patient to aseries of accommodation tasks of varying diopters. For example, anaccommodation task protocol may involve adjusting the viewing conditionso as to subject the patient to sequential diopters of ½ D, ¼ D, ½ D, ¾D, 1 D, ¾ D, ½ D, ¼ D, 0 D, and so on. Again, the viewing condition canbe adjusted by adjusting a trial lens system or by adjusting a targetdistance. The viewing conditions can be varied in any way desired. Insome cases, the viewing conditions may include a protocol providingsequential diopters in 0.1 D increments. Parameters of the method can beadjusted according to the desired or required degree of accuracy.

A presbyopia application may involve adjusting the viewing conditions soas to provide a continually increasing diopter protocol to the patient.Such a protocol may include, for example, sequential diopters of ¼ D, ½D, ¾ D, 1 D, 1¼ D, 1½ D, and so on. As noted previously, the protocolcan be metered in 0.1 increments. Thus, step 200 may involve obtainingan induced pupil size for the eye that corresponds to a ¼D viewingcondition, step 205 may include adjusting a trial lens or a targetdistance to change the viewing condition from ¼ D to ½ D, and step 210may include obtaining an induced pupil size for the eye that correspondsto the ½ D viewing condition. In an exemplary embodiment, the viewingcondition can be adjusted until the patient's pupil size, or sphericalaberration, or some other metric, ceases to change or meets a certainthreshold or value. Similarly, the viewing condition can be changeduntil the difference between certain induced metrics meets or exceeds acertain threshold or value Accordingly, step 215 includes comparing theinduced metric of step 210 with the previous induced metric of step 200.In the case of a pupil size measurement, if the difference between afirst viewing condition pupil size and a second viewing condition pupilsize is sufficiently large, then the method may involve reiteratingsteps 205, 210, and 215. If the difference between the previous viewingcondition induced metric and the subsequent viewing condition inducedmetric is not sufficiently large or does not meet or exceed a certainthreshold, then method 500 can include determining an accommodationcharacteristic of the eye as indicated by step 225. The accommodationcharacteristic can encompass, for example, a maximum accommodation ofthe eye or a minimum accommodation of the eye. In some cases, theviewing condition is adjusted, and the induced metric is monitored,until the induced metric no longer changes even under continuedadjustments in the viewing condition. In some cases, the induced metriccan be modulated or effected by changing the distance of the viewingtarget. Relatedly, a viewing condition can include a vergence testing ortreatment parameter, which can be varied during examination ortreatment. Similar viewing conditions are discussed in co-pending andcommonly owned U.S. patent application Ser. No. 10/872,331 filed Jun.17, 2004, and Ser. No. 11/156,257 filed Jun. 17, 2005, the contents ofwhich are incorporated herein by reference. In some embodiments, it maybe desirable to evaluate or treat an eye under a vergence condition thatis zero or close to zero, or that is at some other value. A vergence canbe based on a reciprocal of a target distance. Based on such procedures,it is possible to determine whether the eye is minimally accommodated ormaximally accommodated. The method may involve determining whether thecorresponding induced metrics, for example pupil size or sphericalaberration, have reached a certain expected value or level. In somecases, if the difference between the previous viewing condition inducedmetric and the subsequent viewing condition induced metric is notsufficiently large or does not meet or exceed a certain threshold, thenmethod 500 can optionally include iterating steps 205, 210, and 215 asindicated by step 220.

In the case of a maximally accommodated eye, the method may includeadjusting the trial lens to sequentially increase (e.g. in 0.1 D or 0.25D increments) the diopter for the viewing condition, and using a videocamera to track and measure the corresponding pupil size changes. Atsome point, the pupil size ceases to change, even as the viewingcondition continues to be adjusted. In this way, the method encompassesforcing the eye to the limit to determine a forced maximumaccommodation. In a preferred embodiment, ambient light is maintained ata constant during this procedure, as changes in ambient light may havean effect on pupil size.

In the case of a minimally accommodated eye (or a maximallyunaccommodated eye), the method may include adjusting the trial lens tosequentially decrease (e.g. in 0.1 D or 0.25 D increments) the diopterfor the viewing condition, and using a video camera to track and measurethe corresponding pupil size changes. Typically, decreasing powerviewing conditions are associated with increasing pupil size dimensions.At some point or threshold, the pupil size reaches a maximum level anddoes not increase, even as the viewing condition continues to beadjusted. This can be the stage where accommodation is completely ormaximally relaxed. The adjustments of the viewing conditions and themeasurement of the induced metrics can be automated by software.

As an illustrative example, it is helpful to consider subjecting apatient to a variety of viewing conditions so as to determine anaccommodation characteristic of the patient's eye, such as a maximumaccommodation or a minimum accommodation of the eye. For example, theviewing condition can be adjusted so as to subject the patient to aseries of increasing diopters values, and the induced metric ceases tochange when the viewing condition reaches 2 D, then it may be possibleto determine that the patient has 2 D of residual accommodation. Whendetermining a minimum accommodation of the eye, the viewing conditionstypically include a progression toward decreasing diopters. Relatedly,when determining a maximum accommodation of the eye, the viewingconditions typically include a progression toward increasing diopters.

Presbyopia Treatment

Method 500 can also include determining a residual accommodation of aneye based on characteristics of the eye in a maximally accommodated orhighly accommodated state as indicated by step 240. Residualaccommodation can be related to the trial lens power or the targetdistance. Residual accommodation can be based on a power that isdetermined by the reciprocal of the target distance. As a person ages,the ability to accommodate typically diminishes. Residual accommodationreflects a measure of the accommodative capacity that a patient retains.Thus, a patient having a lower degree of residual accommodation exhibitsmore severe presbyopia, whereas a patient having a higher amount ofresidual accommodation exhibits less severe presbyopia. For example, aneye having one diopter of residual accommodation may allow a patient toimage with good acuity anywhere throughout a one-diopter target distancerange. Residual accommodation is also discussed in U.S. patentapplication Ser. No. 11/134,630 filed May 19, 2005, the entire contentof which is incorporated herein by reference. It may be desirable toinclude the amount of residual accommodation in the design of apresbyopic treatment so the patient may achieve an optimal outcome. Themethod may also include a screening step, whereby a determination ismade whether to treat the patient based on the residual accommodationmeasurement. In many cases, it may be easier or more desirable tooptimize a treatment shape for a patient having a higher residualaccommodation. Embodiments of the present invention encompass screeningsystems and methods for choosing or selecting IOLs. For example, anoptical apparatus can include an IOL or accommodating IOL placed in theoptical path, and the IOL or accommodating IOL can be used as part ofthe optical element in the optical bench. Subjective testing can beperformed for screening purposes, and this can be done prior to surgeryor treatment.

As shown by steps 250 and 255, the method may also include obtainingaberration data, for example with a WaveScan device or the like, anddetermining a presbyopia treatment based on the residual accommodationand the aberration data. Embodiments of the present invention encompassscreening systems and methods that determine whether to proceed with acorneal ablation treatment based on the residual accommodation of thepatient. For example, if the residual accommodation of the patient asdetermined in step 240 is sufficiently large, the technique may involveproceeding with an ablative treatment. Conversely, if the residualaccommodation is sufficiently small, the technique may involverefraining from administering an ablative treatment to the patient. Insome cases, the threshold residual accommodation is about 0.5 Diopters,whereby if the patient has a residual accommodation greater than about0.5 D, an ablative treatment is administered to the patient, but if theresidual accommodation is less than about 0.5 D then the patient isprovided with a multifocal IOL. Techniques may involve aspects ofresidual accommodation and threshold residual accommodation which arediscussed in co-pending and co-owned U.S. patent application Ser. No.11/134,630, the contents of which are incorporated herein by reference.

In this way, the residual accommodation can be used to determine anappropriate or desired treatment modality for a presbyopic patient. Forexample, in presbyopes having a larger amount of residual accommodation,it may be desirable to administer a corneal reshaping treatment. Inpresbyopes having a smaller amount of residual accommodation, it may bedesirable to treat the patient with a multifocal IOL. Thus, thedetermination can be made based on the residual accommodation of thepatient, and independently of the age of the patient.

In some cases, when designing a presbyopia prescription shape based onthe residual accommodation, it may be desirable to design the shape soas to maintain a substantial or maximal degree of distance vision.However, there is often a trade off as presbyopia correction typicallyinvolves a compromise between optimal near vision and optimal distancevision. For example, in an older patient having less residualaccommodation, it may be desirable to administer a treatment thatincludes a slightly higher spherical aberration, thus providing anincrease in near power (near vision) but a decrease in far power(distance vision). In a patient having more residual accommodation, itmay be desirable to administer a treatment that includes a lessaggressive aspheric component, thus providing less of an increase innear power and less of a decrease in far power. Often, the process ofdesigning a prescription shape includes decisions regarding themanagement of simultaneous near and far vision, as well as whether thenear vision meets or approaches a desired threshold or standard.

CustomVue Procedure

The WaveScan wavefront diagnostic system measures aberrations of theocular optical system. Based on wavefront measurements, the systemgenerates graphic displays of those aberrations, generates mathematicalmodels of the aberrations, and transmits aberration data for use by aVISX laser eye surgery system. In addition to standard optical defectssuch as myopia, hyperopia, and cylindrical astigmatism, this diagnostictool provides objective measurements of higher-order aberrations of theeye. VISX laser eye surgery systems can direct ablative laser energyfrom an excimer laser toward a cornea of a patient. A processor of theVISX laser system can direct a pattern of the ablative energy toward thecorneal tissue so as to alter the shape of the cornea, effectivelychanging the shape of the corneal lens. The corneal stroma isselectively ablated by the laser energy so as to resculpt the cornea,modifying the refraction provided by the cornea itself. In a CustomVuetreatment procedure, the pattern of ablative energy is derived from thewavefront aberration data measured by the WaveScan wavefront diagnosticsystem so as to correct low and high-order aberrations of the eye,thereby providing a corrected visual performance that often exceeds thatavailable through standard corrections such as off-the-shelf spectaclesor contacts.

Method 500 can also include determining a target metric based on aminimum accommodation characteristic of an eye, as indicated by step245. This approach includes pushing the eye to or toward anunaccommodated or minimally accommodated state. For example, theapproach may involve asking or forcing the patient to accommodate, via atrial lens system or a changing target distance protocol, so as toinduce sphere in the eye. Then, the distance between the patient and thetarget can be decreased, or the trial lens system can be adjusted towarddecreasing powers, so as to reduce the plus lens. Eventually the patientwill approach or reach an unaccommodated or minimally accommodatedstate. The target metric can be calculated based on the unaccommodatedor minimally accommodated state of the eye.

As indicated in step 300, the method may also include determining anactual metric of the eye. For example, a video camera can be used todetermine the actual, and in some cases real time, pupil size ordimension of the eye. Similarly, a Hartmann-Shack device can be used todetermine an actual spherical aberration of the eye. Step 305 includesdetermining whether or to what degree the actual metric meets orapproaches the target metric. This step may involve determining whetherthe eye is unaccommodated or minimally accommodated. In this way, anoperator can ensure that the examined eye is unaccommodated, minimallyaccommodated, or the like, which may indicate that instrument myopia isno longer induced, and that there is no vergence. The determination canbe based on aberration data, the pupil size, or some other data. Thistechnique is helpful in decreasing or eliminating error in situationswhere the patient's eye is continuing to accommodate somewhat. Incertain CustomVue treatments, when the eye accommodates the reportedwavescan is not accurate for sphere or spherical aberration, and it maybe difficult to determine whether the eye is unaccommodated as desired.In some cases, the determination of an unaccommodated state may bedifficult because of microaccommodation and the tear film fluctuations.Embodiments of the present invention provide a systematic way ofcompelling the patient toward an unaccommodated state.

According to embodiments of the present invention, it is thereforepossible to monitor the actual metric (e.g. pupil size) to determinewhether or to what extent the eye of the patient is approaching anunaccommodated or minimally accommodated state. If the actual metricdoes not meet the target metric, the method may include adjusting theviewing condition so as to push the eye toward a more accommodated stateor toward a less accommodated state. This can be accomplished with atrial lens system, a moving target, a simulated moving target, and thelike. The method may also include providing a signal to the operatorindicating whether a maximally or highly unaccommodated state is reachedor maintained. Further, the method may include making a decision whetherto proceed with an ocular aberration measurement or not, based onwhether or to what degree the actual metric approaches or meets thetarget metric, as indicated by step 310. As noted previously, the targetmetric can be determined by step 120 (based on natural metric) or bystep 245 (based on minimum accommodation characteristic).

The ocular aberration measurement of step 310 may include a wavescanexam. For example, if the actual accommodation state of the eye meetsthe target accommodation state, the method proceeds with a fullwavefront scan. Typically, the trial lens is removed from the opticalpath prior to taking the aberration measurement. Embodiments of thepresent invention encompass techniques that involve compelling the eyetoward a deaccommodated state, and measuring a wavefront of the eye whenthe eye is in a minimally accommodated state.

In this way, it is possible to ensure that the accommodation state ofthe eye is known when the ocular aberration measurement is taken. Forexample, it may be desirable to ensure that the eye is unaccommodated orsubstantially unaccommodated when a wavescan exam is performed. In somecases, it may be possible to proceed directly to ocular aberrationmeasurement of step 310 after determining that threshold is not exceededin step 225.

As shown in step 315, the method may include alerting a system operatorif the actual metric does not meet the target metric. For example, thepatient may not be sufficiently deaccommodated. Optionally, the methodmay include adjusting the viewing condition in an attempt to change theactual metric of the eye, as indicated by step 317. The method may theninclude returning to step 300 to determine the actual metric of the eye.

Thus, embodiments of the present invention provide a series ofpre-examination measurements, whereby a method may encompass performinga series of preliminary validation steps prior to the aberrationmeasurement. Typically, these tests involve induced vergence or inducedmyopia. In order to ascertain the desired parameters, such as the stateof a minimally accommodated eye, the method may involve pushing the eyetoward a less accommodated state or a more accommodated state. When thepretesting is complete, the testing optics can be removed and theaberration measurement can proceed. In a typical scenario, prior to awavefront exam a patient is subjected to a trial lens protocol thatpushes the eye from a more accommodated state toward a less accommodatedstate. If the patient eye does not reach a desired level ofunaccommodation, the method may include providing a warning message tothe system operator that the eye is not sufficiently unaccommodated. Ifthe patient eye reaches the desired level of unaccommodation, the methodmay include proceeding with a wavescan exam. The method may or may notinclude removing the optical testing apparatus from the optical pathprior to the aberration measurement. For example, when evaluating apupil size metric, it may be possible to leave a trial lens in theoptical path. Conversely, when evaluating a spherical aberration metric,it is often desirable to remove a trial lens from the optical path priorto performing the ocular aberration measurement.

In some embodiments, a method may include measuring a plurality ofspherical aberrations to determine an accommodation profile of an eye.In this way, it is possible to determine an ocular aberration relativeto a spherical aberration structure.

FIGS. 6A-6C illustrate the effects of changing focal distance on apatient's lens. In some cases, a large pupil size may be beneficial incapturing such information. SA measurements may be used to characterizeor predict the hardness of a nucleus. It is possible to derive aspherical aberration of a nucleus based on a total ocular sphericalaberration and a topography measurement of spherical aberration of acornea. Embodiments provided herein encompass models which reflect aperson's age, the hardness of the nucleus, and the spherical aberration.For example, it is possible to build a model where as a person ages, anucleus becomes harder, and spherical aberration increases. Models maybe constructed from population studies, to support predictions ofnucleus characteristics, such as hardness, based on spherical aberrationmeasurements. A human crystalline lens consists of material having agradient index of refraction. Spherical aberration and other aberrationparameters can change during accommodation, as well as duringmini-accommodation or micro-accommodation, because of the correspondingchange in shape of the crystalline lens. Thus, accommodation involves achange in lens shape accompanied by a change in optical aberrations. Forexample, a lens in a less accommodated state can be flatter, having alower diopter and higher focal length. In contrast, a lens in a moreaccommodated state can be more round, having a higher diopter and asmaller focal length. In an unaccommodated state, the sphericalaberration of the eye or lens is relatively small. When the eyeaccommodates, the shape of the lens becomes more round or bulging, thusincreasing the amount of spherical aberration. Typically, as a personages the capacity for the eye to accommodate diminishes. It has alsobeen observed that the pupil constricts as the eye accommodates.However, in many cases the amount of pupil constriction is independentof the patient's age. FIG. 6A shows a target 610 a at or near opticalinfinity, with a high focal distance D_(a). Accordingly, lens 620 b isrelatively flat, has a low diopter, and is in a more relaxedaccommodation state. FIG. 6B shows a target 610 b that is closer to theeye, with a medium focal distance D_(b). Accordingly, lens 620 b issomewhat bulging. FIG. 6C shows a target 610 c that is very close to theeye, with a short focal distance D_(c). Accordingly, lens 620 c has ahighly bulging shape. The sphere and spherical aberration componentstypically change in these situations. For example, the sphere andspherical aberration can be relatively small in FIG. 6A, intermediate inFIG. 6B, and relatively large in FIG. 6C. As FIGS. 6A-6C illustrate, asa target moves closer to the eye, the lens adopts a greater curvature soas to keep the target in focus. In a presbyopic patient, the ability totransition from a flatter lens to a bulging lens is diminished. Thus,the lens remains flatter, even when the patient is trying to gaze at anear distance, for example when reading a newspaper.

In many optical procedures where the patient is subject to the influenceof optical testing machinery, it may be difficult or impossible for thepatient to completely relax the lens of the eye. Accordingly, there isoften some accommodation, which may be referred to as instrument myopia.This instrument myopia may be present even when the patient is trying tosuppress the accommodation. Hence, optical measurements that aredesigned to reflect the status of the eye may include some amount ofaccommodation. It is useful to characterize the relationship between anoptical measurement and the accommodation of the eye. FIG. 7Agraphically illustrates a relationship between a spherical aberration (yaxis) and an accommodation state (x axis) of the eye. An exemplaryprocedure may include monitoring the patient's wavefront scan under avariety of different viewing conditions, for example a series ofaccommodation tasks. A metric such as spherical aberration can bedetermined from the wavefront, and synchronized or correlated with theaccommodation tasks. As shown here, as the eye becomes more accommodatedin response to changing viewing conditions. The increase or change inaccommodation can be in response to, for example, a stimulus such as anoptical testing apparatus, which induces the amount of sphericalaberration in the eye to increase or otherwise change. A first inducedspherical aberration can be represented by point A, and a second inducedspherical aberration can be represented by B.

In one illustrative example, a patient accommodates to a target and awavefront measurement is taken. The target is then moved, and anotherwavefront measurement is taken. This can be driven by known change insphere. For example, a target distance can be moved from 1 meter to 2meters, or from 1 meters to 0.5 meters, or the like. Similarly, a targetdistance can be fixed and a trial lens can be manipulated by changingthe sphere. This can provide a similar effect to changing the targetdistance or vergence viewing condition. By analyzing the wavefrontreadings, it is possible to correlate a change in ocular aberration withthe state of accommodation in the eye. A wavefront measurement or metriccorresponding to the unaccommodated eye (e.g. zero accommodation) can beextrapolated or determined based on this correlation.

A relationship between spherical aberration and accommodation can beestablished based on the induced metrics, and the relationship can beused to determine or predict metric values at various levels ofaccommodation. For example, it is possible to predict or extrapolate thespherical aberration at point C, which corresponds to the eye in theunaccommodated state. Zero accommodation is analogous to eye gaze atinfinity. A similar approach can be used to predict or extrapolate apatient's pupil size or dimension for a given amount of accommodation.Related methods include qualifying a certain wavefront measurement outof several wavefront measurements.

FIG. 7B graphically illustrates a relationship involving residualaccommodation and range of accommodation.

A residual range of accommodation can be quantified or configured, andalgorithms can derive a presbyopia shape.

Parameters for design include the Residual Range of Accommodation, whichmay be particularly useful for designing a presbyopia treatment. Pupildynamic parameters can also be used in the design of a presbyopiatreatment.

Based on data from the relationship shown in FIG. 7B, it is possible todetermine an optimal accommodation pattern for a specific patient, andtherefore it is possible to determine an optimal vision correctiontreatment for the patient. In some cases, the vision treatmentencompasses a treatment for presbyopia. For example, some patients maybenefit from a reduced amount of add in the presbyopic correction. Asdepicted in FIG. 7B, residual accommodation is represented by theportion where the line levels off horizontally, which corresponds to amaximally accommodated eye.

FIG. 7C graphically illustrates a relationship involving opticalcharacteristics of an eye. The point A represents a typical or normalpatient. Point B represents an older patient that has presbyopia. Atypical wavefront aberration includes contributing factors such as alenticular aberration (or lens aberration) and a corneal aberration.Often, however, it is difficult to determine from a wavefront scan whichwavefront aberrations derive from lenticular aberrations and whichderive from corneal aberrations. It may be desirable to characterize thecontributing factors of the wavefront. One approach involves theassumption that the corneal aberrations are known, and that thelenticular aberrations vary in response to changing viewing conditionsor stimuli. Hence, it is possible to evaluate changes in the wavefrontthat occur in response to the viewing conditions, and attribute thesechanges to lenticular aberrations. Based on this approach, it ispossible to determine what factors contribute to a wavefront aberration.

Advantageously, it has been discovered that through-focus measurementsof an ocular wavefront can be used to derive accommodation-freerefraction, and thus lenticular (lens) contribution to ocular wavefrontcan be determined, for example based on a combination of topographicdata and ocular wavefront measurement data, it is possible to derive alenticular contribution.

FIG. 7D graphically illustrates a relationship between an accommodationstate (y axis) and a pupil size or dimension (x axis) of the eye. Anexemplary procedure may include monitoring the patient's eye under avariety of different viewing conditions. The viewing conditions mayencompass a series of accommodation tasks. The method may also includecorrelating the pupil dimension metric with the accommodation status. Asshown here, an increase in pupil dimension is correlated with a decreasein the level of accommodation in the eye. A relationship betweenaccommodation and pupil size can be established based on these values.It is therefore possible to extrapolate to determine a pupil size thatcorresponds to a zero accommodation state of the eye. Often,determination of an accommodation-free pupil size is achieved underconsistent, calibrated ambient lighting. Thus, lighting can becalibrated for pupil size purposes. Based on the data provided by FIG.7D, it is possible to determine an accommodation value for a particularpupil size.

As shown in FIG. 7D, a maximum accommodation state of the eye cancorrespond to a minimum pupil size of the eye, and this can bedetermined by adjusting an accommodation target or stimulus. Based onthis data, it is possible to calculate the residual accommodation, whichcan be described as the amount of accommodation that remains in the eye.The residual accommodation can be calculated based on a distance betweenthe eye and the target. Patients having more severe presbyopia have lessresidual accommodation Patients with milder presbyopia have moreresidual accommodation. Pupil size thus can be an independent indicatorof accommodation.

FIG. 7E graphically illustrates a relationship between a sphericalaberration (y axis) and a pupil size or dimension (x axis) of the eye.An exemplary procedure may include monitoring the patient's pupil sizeunder a variety of different viewing conditions, for example a series ofaccommodation tasks. A metric such as pupil diameter can be determinedby a video camera, and synchronized or correlated with the sphericalaberration, which may be determined based on a wavefront scan. As shownhere, an increased pupil size correlates with a decreased sphericalaberration. A relationship between spherical aberration and pupil sizecan be established based on these values.

FIG. 8 depicts relationships between accommodation, pupil size, and netspherical aberration according to embodiments of the present invention.In an exemplary technique, a series of accommodations tasks is given toa patient, and a corresponding series of wavefront measurements istaken. As the accommodation response results in a change of the eyelens, characteristic ocular aberrations such as sphere (defocus),spherical aberration (shape change), and coma (lens decentration) can becorrelated with different values of the wavefront bias or spherical biasdue to instrument myopia. Aberrations can also be correlated withdifferent values of pupil size. These metrics can be used to determine aprescription for an optimal IOL, an accommodating IOL, and the like, orfor the derivation of design parameters for a multi-focal presbyopiccorrection on the cornea. For example, a spherical aberration metric ora pupil metric can be used to design an optimal IOL or an accommodatingIOL. A population mean can be determined, and an IOL design can beoptimized so as to correct or treat a certain amount of sphericalaberration for an optimal or specific pupil size. As shown here, as thediopter of the accommodation task increases, the spherical aberrationincreases, and the pupil size decreases. By determining a relationshipbetween these factors, it is possible to derive the accommodation zeropoint from the line based on the mesopic pupil size of the patient,where the mesopic pupil size corresponds to the eye is a normalunaccommodated condition. In some embodiments, it is possible to traindown the spherical aberration line, and determine a point where amountof spherical aberration no longer changes when a trial lens power isreduced. This is a point where it is possible to derive theaccommodation. In some embodiments, residual accommodation may be usedto determine the amount of accommodation desired for an accommodatingIOL. It is also possible to design aberration corrections into anaccommodating IOL to reduce changing aberrations as the eyeaccommodates. An amount of spherical aberration can be predesigned foran IOL, such that when the IOL is in an accommodating situation, anamount of spherical aberration is provided for a desired or optimalperformance. If the eye exhibits non-linear accommodation, it may bepossible to design an accommodating IOL to compensate.

FIG. 9 depicts relationships between accommodation, pupil size, and netspherical aberration according to embodiments of the present invention.A series of accommodations tasks is given to an IOL patient, and acorresponding series of wavefront measurements is taken. The pupil sizedecreases as the diopter of the accommodation task increases. However,because it may be difficult or impossible for an IOL patient toaccommodate, the spherical aberration is observed to decrease as thediopter of the accommodation task increases.

Embodiments of the present invention are well suited for use indesigning and developing custom multifocal IOLs, corneal inlays andonlays, and contact lenses. Embodiments of the present invention alsoencompass systems and methods for developing and designing IOLs andaccommodating IOLs. For example, it is possible to evaluateaccommodating IOLs after implantation to determine the optimal ordesired amount of spherical aberration for an IOL. Data can be re-inputor reiterated to refine accommodating IOLs. A population study can beperformed for patients who have received implants. Data from the studycan be used to determine a spherical aberration that is helpful for apatient. For example, it is possible to determine an amount of sphericalaberration for a certain type of accommodating IOL. In many currentsituations, accommodating IOLs do not include a gradient index material.If an accommodating IOL includes a gradient index material or involves atwo piece optic accommodating IOL, there may be a change of sphericalaberration. This can mimic a real natural crystalline lens, and can beused for similar studies.

Typically a lens of an eye exhibits a varying gradient index ofrefraction. In contrast, a polymer-filled bag often has a uniform indexof refraction.

Each of the above calculations or operations may be performed using acomputer or other processor having hardware, software, and/or firmware.The various method steps may be performed by modules, and the modulesmay comprise any of a wide variety of digital and/or analog dataprocessing hardware and/or software arranged to perform the method stepsdescribed herein. The modules optionally comprising data processinghardware adapted to perform one or more of these steps by havingappropriate machine programming code associated therewith, the modulesfor two or more steps (or portions of two or more steps) beingintegrated into a single processor board or separated into differentprocessor boards in any of a wide variety of integrated and/ordistributed processing architectures. These methods and systems willoften employ a tangible media embodying machine-readable code withinstructions for performing the method steps described above. Suitabletangible media may comprise a memory (including a volatile memory and/ora non-volatile memory), a storage media (such as a magnetic recording ona floppy disk, a hard disk, a tape, or the like; on an optical memorysuch as a CD, a CD-R/W, a CD-ROM, a DVD, or the like; or any otherdigital or analog storage media), or the like.

While the exemplary embodiments have been described in some detail, byway of example and for clarity of understanding, those of skill in theart will recognize that a variety of modification, adaptations, andchanges may be employed. Hence, the scope of the present inventionshould be limited solely by the claims.

What is claimed is:
 1. An apparatus for determining an appropriatepresbyopia treatment modality for an eye of a patient, the eye having avision deficiency, the apparatus comprising: a first input configured toreceive a first induced metric for the eye that corresponds to a firstviewing condition; a second input configured to receive a second inducedmetric for the eye that corresponds to a second viewing condition; afirst module configured to determine the difference between the firstinduced metric and the second induced metric; a second module configuredto determine an accommodation characteristic of the eye if thedifference between the first induced metric and second induced metricdoes not exceed a predetermined threshold; a third module configured todetermine a residual accommodation of the eye based on the accommodationcharacteristic; a fourth module configured to receive an ocularaberration measurement of the eye; and a fifth module configured todetermine a presbyopia treatment modality for the eye based on theresidual accommodation and the ocular aberration measurement.
 2. Theapparatus of claim 1, wherein an ablative treatment modality is selectedif the residual accommodation of the patient is greater than thethreshold amount of about 0.5 Diopters.
 3. The apparatus of claim 1,wherein a multifocal intraocular lens is selected if the residualaccommodation of the patient is less than the threshold amount of about0.5 Diopters.
 4. An apparatus for determining an intraocular lenstreatment for administration to the eye of a patient, the apparatuscomprising: a first input configured to obtain a corneal aberrationmeasurement corresponding to a corneal plane of the eye of the patient;a second input configured to obtain an ocular aberration measurement ofthe eye, the ocular aberration measurement based on a first inducedmetric for the eye that corresponds to a first accommodation state ofthe eye and a second induced metric for the eye that corresponds to asecond accommodation state of the eye; and a first module configured todetermine the aberration of the lens based on a difference between thecorneal aberration measurement and the ocular aberration measurement,wherein the difference is represented at a peripheral lens plane of theeye of the patient.
 5. The apparatus of claim 4, further comprising asecond module configured to determine a prescription of an intraocularlens for the treatment.
 6. The apparatus of claim 5, wherein theintraocular lens prescription is based on the ocular aberrationmeasurement of the lens.
 7. The apparatus of claim 4, wherein the firstinput is a topography device.
 8. The apparatus of claim 4, wherein thefirst induced metric comprises a first induced spherical aberration ofthe lens and the second induced metric comprises a second inducedspherical aberration of the lens.
 9. The apparatus of claim 4, furthercomprising a third module configured to determine a treatment for theeye of the patient based on the aberration of the lens.
 10. Theapparatus according to claim 9, further comprising a fourth moduleconfigured to provide treatment to the eye of the patient.
 11. Anophthalmic laser surgery system for treating presbyopia in an eye of apatient, the laser surgery system comprising: a computer including: a)processor configured to communicate with at least one peripheral devicevia a bus subsystem; wherein the peripheral device includes a memorysubsystem, a file storage subsystem, a user interface input device, auser interface output device or a network interface subsystem; b) anetwork interface subsystem configured to communicate to outsidenetworks; c) a wavefront measurement system, wherein the wavefrontmeasurement system includes: a) a first input configured to receive afirst induced metric for the eye that corresponds to a first viewingcondition; b) a second input configured to receive a second inducedmetric for the eye that corresponds to a second viewing condition; c) afirst module configured to determine the difference between the firstand the second induced metrics represented at a lens plane of the eye ofthe patient; and a laser coupled to the computer and adapted to providetreatment to the eye of the patient based on the difference between thefirst induced metric and the second induced metric.